Our objectives are to understand the bases of recoveries of functions after cerebral injuries. The systems we study are hooded rats prepared with lesions of the visual cortex. The lesions typically produce impairments of postoperative retention of brightness habits and, in our experience, absolute impairments of learning of visual-pattern habits. We have shown that the losses of postoperative retention of the brightness habits are failures of remembering or retrieval. We think of them as models for memorial impairments which are seen in human patients with strokes, and have long searched for methods of correcting the losses by methods other than re-education in the hope that rationales for pharmacological managements of patients with strokes can be developed. The failures of retention of brightness habits, are very much reduced if the subjects are prepared with successive partial cortical ablations and retrained between the two operations. A minimal interval of time must elapse, and Goodman and Horel have proposed that that requirement reflects times of sproutings of visual-tract axons and establishments of new visual pathways. We are essentially examining the strongest predictions of the Goodman-Horel theory throught a combination of neurobehavioral and neuroanatomical procedures. BIBLIOGRAPHIC REFERENCES: Meyer, D.R., Hughes, H.C., Buchholz, D.J., Dalhouse, A.D., Enloe, L.J. and Meyer, P.M. The comparative effects of simultaneous bilateral and successive unilateral frontal cortical ablations upon delayed alternations and delayed responding in monkeys. Brain Research, 1976, 108, 397-412. Bresnahan, J.C., Meyer, P.M., Baldwin, R.B. and Meyer, D.R. Avoidance behavior in rats with lesions in the septum, fornix longus, and amygdala. Physiological Psychology, 1976, in press.